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According to Johnson and Morton, there are two visual pathways for face detection: the primary cortical pathway and one through SC and pulvinar.

The cortical pathway is called CONLEARN and is theorized to be plastic, whereas the sub-cortical pathway is called CONSPEC and is thought to be fixed and genetically predisposed to detect conspecific faces.

Anastasio and Patton present a model of multi-sensory integration in the superior colliculus which takes into account modulation by uni-sensory projections from cortical areas.

In the model due to Anastasio and Patton, deep SC neurons combine cortical input multiplicatively with primary input.

Anastasio and Patton's model is trained in two steps:

First, connections from primary input to deep SC neurons are adapted in a SOM-like fashion.

Then, connections from uni-sensory, parietal inputs are trained, following an anti-Hebbian regime.

The latter phase ensures the principles of modality-matching and cross-modality.

Many of the cortical areas projecting to the SC have been implicated with attention.

The most important cortical input to the SC (in cats) comes from layer V cortical neurons from a number of sub-regions of the anterior ectosylvian sulcus (AES):

  • anterior ectosylvian visual area (AEV)
  • the auditory field of AES (FAES)
  • and the fourth somatosensory area (SIV)

These populations in themselves are uni-sensory.

Neurons that receive auditory and visual ascending input also receive (only) auditory and visual descending projections.

There are monosynaptic excitatory AES-SC projections and McHaffie et al. state that "the predominant effect of AES on SC multisensory neurons is excitatory."

Cognitive factors can influence multisensory processing.

Semantical congruence can influence multisensory integration.

Different parts of the visual field feed into the cortical and subcortical visual pathways more or less strongly in humans.

The nasal part of the visual field feeds more into the cortical pathway while the peripheral part feeds more into the sub-cortical pathway.

In one experiment, newborns reacted to faces only if they were (exclusively) visible in their peripheral visual field, supporting the theory that the sub-cortical pathway of visual processing plays a major role in orienting towards faces in newborns.

It makes sense that sub-cortical visual processing uses peripheral information more than cortical processing:

  • sub-cortical processing is concerned with latent monitoring of the environment for potential dangers (or conspecifiics)
  • sub-cortical processing is concerned with watching the environment and guiding attention in cortical processing.